There is a way to share DLC (downloadable content) to more than one XBox. It is a little known trick to get it working. Some people have multiple XBox 360’s in the home, with two XBox Live accounts. Here is how to buy DLC once, and apply it to both Xboxes.
1. First, you go to the second console (the one you don’t play all the time). Sign in using YOUR Xbox Live account (use the Recover Gamertag option). Puchase the DLC and download it to that console. Sign out of XBox Live. Everyone that logs into the console will have access to the DLC.
2. Now, go to your main console and sign into your account (you may need to use the Recover Gamertag, if needed). Download the DLC again. You will get a notice that you already puchased the content and ask if you want to download it again. Choose Yes. It will download it and you will have the DLC on both consoles. Only the XBox Live account that downloaded the content will be able to use it.